Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

__________________________________________________________________________________Major Diseases of Eggplant3-A.8. Steam sterilization to manage leaf spot diseases in the nursery3-A.9. Test effect of infected crop debris in the field3-A.10. Effect of rain on the spread of leaf spot3-A.12. Test different cultivars for resistance to leaf spot3-A.13. Pruning and plant compensation study3-A.14. Restricted fungicide use to manage leaf spots3-C.1. Symptom development of fruit diseases: classroom exercise3-C.2. Symptom development of fruit diseases: field exercise3-C.3. Use of healthy seed3-C.4. Test of seed health8.2.2 Early Blight - Alternaria solaniSee photos 23 and 24 (page 177).Causal organism: fungus - Alternaria solaniThis disease can infect many species of the solanaceous family such as tomato, potato, eggplant, greenpepper, and hot pepper. How early is early blight?The “early” in early blight was used in the U.S.A. to distinguish Alternaria blight from Phytophthora lateblight; it refers to the time of disease appearance relative to plant age. In other countries, early or latedisease appearance may have nothing to do with the causal fungus: early blight may appear late inthe season and late blight may be found at an early growth stage!Signs and symptomsThis disease can be destructive on eggplant at any time inthe life of the plant. It can affect seedlings but is generallyobserved on older plants. All aboveground parts of the plantcan be affected.Seedlings may be affected just before or after emergence.On seedlings, dark spots develop on the seed leaves(cotyledons), stem and true leaves. This seedling dieback isknown as collar rot. Spotted cotyledons may be killed, andspotted stems may be girdled at the base of the plant.Affected seedlings are stunted and may wilt and die. Whenolder seedlings are infected, stem spots usually arerestricted to one side of a stem.Early blight leaf spots on tomato leaf(from: Pandey, 1997)On established plants, dark brown spots with dark concentricrings develop first on oldest leaves. The concentric rings givethe spot a target appearance. Leaf spots are characteristic for early blight. The spots are circular and upto about 1,5 cm in diameter. The spots may occur singly or in largenumbers on each leaf. Yellowish area may develop on affectedleaves and eventually, the leaves turn brown and usually drop fromthe plant. Leaf spotting first appears on the oldest leaves andprogresses upward on the plant. It is possible for entire plants to bedefoliated and killed.In tomato plants, the leaves seem to become susceptible to diseaseattack in the field when the first fruits begin to ripen. It is alsocommon to see disease symptoms appear when the plants areloaded with fruits. It is not clear if this is also true for eggplant. Plantsthat are well fertilized and irrigated are not as susceptible.Early blight fruit spots with fungusspores in concentric rings(from: Pandey, 1997)140Eggplant Ecological Guide